1. Field of the Invention
The present invention relates to novel quaternary ammonium type polymers useful as highly durable anion exchangers and to novel nitrogen-containing fluorocarbon polymers useful as intermediates for the preparation of the quaternary ammonium type polymers. The present invention also relates to processes for preparing such novel polymers.
2. Description of the Prior Art
Anion exchangers, particularly membrane-type anion exchangers, are practically used in the fields of e.g. electrodialysis, diffusion analysis and various electric cells.
For such membrane-type ion exchangers, it has been common to employ a copolymer or a polymer mixture obtainable by a various combination of hydrocarbon monomers, to which anion exchange groups have been introduced by a polymer reaction.
However, such conventional anion exchangers are likely to be materially deteriorated when subjected to severe conditions, for instance, when used in the presence of e.g. chlorine or a strong base, or when subjected to the repetition of swelling and contruction. Therefore, it is desired to develop an anion exchanger which is durable even under such severe conditions.
As a membrane-type anion exchanger developed to improve the durability, there has been known an exchanger prepared by mixing a fluorinated polymer such as poly(tetrafluoroethylene) and an inorganic anion exchanger such as a hydrate of zirconium oxide, and press-molding the mixture (Japanese Unexamined Patent Publication No. 35079/1975). However, the ion exchange capacity of an inorganic anion exchanger composed of such an amphoteric metal oxide is usually largely dependent on the hydrogen ion concentration in the environment in which it is used. In some cases, an inversion of the ion exchange ability will take place. For instance, the hydrate of zirconium oxide acts as an anion exchanger at a pH of 6 or less, but it acts as a cation exchanger at a pH greater than 6 and, it exhibits no substantial ion exchange ability under a neutral condition. Thus, the condition under which the membrane-type anion exchanger comprising such an ion exchanger may be used, is substantially restricted.
It is also known to obtain a durable membrane by fluorinating the surface of a hydrocarbon anion exchange membrane (Japanese Unexamined Patent Publication No. 4489/1977). However, according to this method, it is usually difficult to accomplish adequate fluorination, and it is thereby hardly possible to obtain an anion exchange membrane having adequate properties required for practical industrial purposes.
In view of the superior durability of the fluorinated polymer, the present inventors have conducted extensive researches to develop an anion exchanger using the fluorinated polymer as the base material, and have invented a quaternary ammonium type polymer which is useful as an anion exchanger having superior durability and a process for its preparation. The present inventors have also found novel nitrogen-containing fluorocarbon polymers which are useful as intermediates for the preparation of the quaternary ammonium type polymer, and processes for their preparation.